Spoke too soon. Although the app shows all the devices, a few remain offline. I believe these are older HS105. I tried chatting with a live agent using their support chat, but kept getting bumped...

All my missing devices now show up in the app again.

Same here. I just lost all my smart plugs except a few newer EP25's. Glad I'm not alone, seems like this is a server side issue. I hope this is temporary as I'm away from the house.